Statistical Analysis of Trends in the Red River Over a 45 Year Period

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Executive Summary Statistical evaluation of trends in water quality over a 45-year period will be useful for assessing the effects of variation in precipitation in the Red River watershed and the impact that landscape change has on runoff water quality. The Red River discharges into Lake Winnipeg and the eutrophication of Lake Winnipeg is a research priority of Environment Canada and Manitoba Water Stewardship. This project is supported by the International Red River Board in response to a presentation made by the Canadian Co-Chair of its Aquatic Ecosystems Subcommittee. Statistical trend analysis was performed on the following dissolved ion concentrations: Calcium, Sodium, Potassium, Magnesium, Sulphate, Chloride, total dissolved solids, and specific conductance, as available. Hydrometric stations used for analysis consisted of the Emerson water quality monitoring station, the South Floodway at St. Norbert monitoring station where data were comprised of the sum of the flow from the Ste. Agathe station and the Rat River hydrometric station. The flow data used for the Selkirk monitoring station was gathered from a hydrometric station nine km upstream at Lockport, Manitoba. Concentration data were made available from the Manitoba Water Stewardship and Environment Canada. Streamflow data were gathered from Environment Canada’s Archived Hydrometric data website. Non-parametric and parametric methods were used on the original data and data weighted for flow volume. The non-parametric methods used by Nancy Glozier, Environment Canada were run with WQSTAT v.1.56 and consist of defining hydrologic seasons from concentrations, testing for seasonality using the Kruskal-Wallis test and applying either the xiii
Mann-Kendall or Seasonal Mann-Kendall test for a trend. Seasonality is evident in all water quality parameters, where the minimum data size was met, and in turn the Seasonal Mann-Kendall test was used to test for trend. The Seasonal Mann-Kendall test found significant trends for most constituents except dissolved Chloride at the Emerson station and specific conductance at both the South Floodway and Selkirk monitoring stations. Non-parametric methods do not rely on known probability distributions, in contrast to parametric statistics. There are advantages and drawbacks to both methods as they were used in comparison for trend analysis. Advantages of the Seasonal Mann-Kendall test are: it is easy to compute; has few underlying assumptions and results are not affected by data values lying far beyond the majority of the data (outliers). Disadvantages are: this method assumes a single linear trend; seasons must be defined; flow adjustments must be done separately and they may not be as powerful in detecting trends. Parametric methods were run using QWTREND, developed by Aldo Vecchia, United States Geological Survey, and was used for constituents with enough data to satisfy the requirements of the program. Parametric methods using QWTREND also come with their own advantages and disadvantages. Advantages are: they can be used to model more than just a single linear trend; trends can be explained by magnitude and direction; also with livestock or farming data; streamflow and concentration can be modeled together and QWTREND uses the full power of statistical theories. The drawbacks to these methods are: they are computation intensive; require care in verifying assumptions and require more data than nonparametric methods. A difference in methods that should be noted is that the non-parametric methods compute trends on a linear scale while QWTREND computes log-linear slopes. Both methods were used to analyze the water quality constituents and yielded fairly similar conclusions. Trends in dissolved calcium were highly significant using the non-parametric methods however, significance could not be determined using the parametric method. Trends in dissolved sodium and potassium produced a highly xiv
Page 1 and 2: Statistical Analysis of Trends in t
Page 3 and 4: 5 Comparison of Non-Parametric and
Page 5 and 6: List of Figures 1.1 The Red River B
Page 7 and 8: A.8 Boxplot of Specific Conductance
Page 9 and 10: A.41 Dissolved Calcium Flow Adjustm
Page 11 and 12: A.67 Dissolved Sulphate Flow Adjust
Page 13: A.93 Specific Conductance Flow Adju
Page 17 and 18: Using ancillary data, data obtained
Page 19 and 20: Chapter 1 Introduction The Red Rive
Page 21 and 22: oped by Aldo Vecchia (United States
Page 23 and 24: Chapter 2 Streamflow Data and Conce
Page 25 and 26: Table 2.1: Selected characteristics
Page 27 and 28: of testing for seasonality. If it y
Page 29 and 30: Table 2.3: Sample size of stations
Page 31 and 32: Figure 3.1: Mean monthly streamflow
Page 33 and 34: v.1.56. CAS# n/a WQStat Plus TM BOX
Page 35 and 36: concentrations of major anions and
Page 37 and 38: Table 3.3: Kruskal-Wallis test for
Page 39 and 40: The N ′ individual slope estimate
Page 41 and 42: As most parameters consistently exh
Page 43 and 44: Table 3.4: Seasonal Mann-Kendall Te
Page 45 and 46: Chapter 4 Parametric Methods used f
Page 47 and 48: log denotes the base-10 logarithm;
Page 49 and 50: Figure 4.1: Daily Streamflow at Eme
Page 51 and 52: Figures 4.3-4.8 depict the recorded
Page 53 and 54: 1 1 CONCENTR CONCENTR 1955 1960 196
Page 55 and 56: Table 4.1: Fitted Single Linear Tre
Page 57 and 58: Chapter 5 Comparison of Non-Paramet
Page 59 and 60: 5.2 Future Recommendations First an
Page 61 and 62: • Uses full power of the maximum
Page 63 and 64: Hamed, Khaled.,; 2008, Trend Detect
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Appendix A Figures A.1 Boxplots of
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v.1.56. CAS# n/a WQStat Plus TM BOX
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Figure A.7: Boxplot of Total Dissol
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v.1.56. CAS# n/a WQStat Plus BOX &
Page 73 and 74:
Figure A.13: Seasonality pattern of
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A.3 Non-Parametric Trend Results Th
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Figure A.19: Long term temporal tre
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Page 81 and 82:
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Page 85 and 86:
A.4 Parametric Trend Results The fo
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Figure A.31: Dissolved Sodium at Em
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Figure A.33: Dissolved Magnesium at
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Figure A.35: Dissolved Chloride at
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Figure A.37: Specific Conductance a
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05102500 RED RIVER OF THE NORTH AT
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1 1 CONCENTR CONCENTR 500 RED RIVER
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CONCENTR 500 RED RIVER OF THE NORTH
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CONCENTR ● CONCENTR 0 0 1955 1960
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CONCENTR CONCENTR 00 RED RIVER OF T
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CONCENTR 1 1.5 ! ! ! ! !! ! ! ! ! !
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CONCENTR 0.5 1 ! ! ! ! !! ! !! ! !
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CONCENTR ! ! ! ! ! ! ! ! ! ! ! ! !
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CONCENTR ! CONCENTR 2 2 1955 1960 1
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A.5.2 South Floodway at St. Norbert
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CONCENT ! CONCENT 2 2 floodway dspc
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A.5.3 Selkirk Monitoring Station 10
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CONCENT ! CONCENT 2 2 selkirk dspc
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Statistical Analysis of Trends in the Red River Over a 45 Year Period

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